The sporicidal effect of Presept was compared with Chloramine B on the spores of Bacillus cereus. Either compound was calibrated to the same concentration of active chlorine. While a portion of spore population after 4 hrs of treatment by Chloramine germinated and started to divide in a rich nutrient medium, the optical density of the culture inoculated with spores treated by Presept did not increase even after 7 hrs when exposed to the nutrient medium. Significant morphological differences were found in either population of spores. Spores treated by Presept lost the imperme- ability within 3 hrs in the nutrient medium but almost no postgerminative development was observed. However, a portion of spores treated by Chloramine B developed after germination within 3 hrs into vegetative cells. It seems that Presept does not block germination and/or loss of imperme- ability of spores, but prevents their postgerminative development and division.

        Key words: sporicidal effect – Presept – Chloramine B – disinfection – germination of spores – Bacillus cereus.